A scoping study on coastal vulnerability to relative sea-level rise in the Gulf of Guinea
L. Hauser
Institute of Geosciences and Earth Resources, CNR, Padova, Italy
R. Boni'
Institute of Marine Sciences, CNR, Venezia, Italy
P. Minderhoud
Gamma Remote Sensing, Gumligen, Switzerland
P. Teatini
Dept. of Civil, Environmental and Architectural Engineering, University of Padova, Padova, Italy
M. Woillez
Agence Française de Développement, France
R. Almar
LEGOS, Université de Toulouse, Toulose, France
S. Avornyo
Dept. of Marine and Fisheries Sciences, University of Ghana, Accra, Ghana
K. Appeaning Addo
Institute for Environment and Sanitation Studies, University of Ghana, Accra, Ghana
ABSTRACT
The Gulf of Guinea's low-lying
soft coastline is highly vulnerable
to coastal erosion and relative
sea-level rise (rSLR). Large
capital cities and core economic
activities are concentrated
along the coastline, and
potentially exposed to
unforeseen risk. Currently, there
is limited research on the
impacts and vulnerability to rSLR
(i.e. including land subsidence).
Recent advances in satellite-derived global digital elevation
model (DEM) data offers exciting
opportunities to assess coastal
elevation at large scale and
identify "hotspots" of potential
sea-level rise vulnerability.
Hereto, this study presents first a
literature review on coastal
vulnerability to rSLR in the Gulf of
Guinea region. Secondly, this
study use recent global satellite-based DEMs for a coastal
elevation assessment of the Gulf
of Guinea to identify low-lying
geographical areas needing
more detailed investigations.
Findings from satellite remote
sensing are validated with in-situ
data points in the Volta Delta.
The results from the literature
review highlights that very few
publications investigate the
combined effects from global
SLR and land subsidence in the
studied area. None investigates
the drivers of land subsidence.
Our analysis on satellite-based
DEMs shows that there are large
uncertainties on coastal
elevation in the area, with
considerable discrepancies
between DEMs (>1m). These
results highlight the importance
of validation, either through
ground-truthing or advanced
approaches such as
incorporating multiple DEMs.
Unfortunately, field data that can
be used as reference are scarce
in the region, emphasizing the
need for more field
measurements and publicly
available data. Incorporating
newer data - e.g. LiDAR or high
resolution optical
stereogrammetry - is expected
to improve assessments
significantly and should be
further explored. Based on the
combination of FABDEM and
CoastalDEM_v2.1, several coastal
hotspots of vulnerability to SLR
have been identified, including
Lagos, Niger Delta, Cotonou,
Western Accra, the Volta region,
and urban areas surrounding
the Ebrie lagoon within Abidjan.
We conclude our study with
concrete suggestions for future
research and projects on rSLR in
the region.
